A razor had not yet touched his face when the youthful 15-year-old presented himself to the recruiting sergeant.

He’d always wanted to be a soldier and, weeks after leaving school, wasn’t going to miss this opportunity to serve his country.

It was August 1913 and Britain was enjoying the last year of peace when Ben Clouting enlisted as a cavalryman with the 4th (Royal Irish) Dragoon Guards.

He imagined travelling the world – but his thirst for adventure would, exactly 12 months later, propel him into the most ­devastating war in history.

To enlist, Ben had to add two years to his age. His deception was far from unique. But what makes him remarkable was he fought in almost every major battle on the Western Front from the first shot at Mons to the last fired near the same town four years later.

Ben was 16 when war was declared in August 1914.

Though legally too young to serve abroad – like the boy hero of the book, play and film War Horse – Ben begged his commanding officer to turn a blind eye. And two weeks later he saw action.

Ben’s story is told in a new book by top historian Richard van Emden, who interviewed hundreds of veterans during their last years.

Richard said: “Many found their experiences too traumatic to talk about. Others told their stories as a warning against the folly of warfare.

“Ben, by contrast, had found the idea of going to war strangely exhilarating.”

He was raised in Sussex on a diet of heroic adventure stories and dreamt of riding a horse into battle.

His dad was head groom at a stables used by cavalry officers such as Adrian Carton de Wiart, who went on to a VC.

When he heard Ben wanted to join up, he invited him into his regiment – which is how the teen was among the first Brits to see action in the Great War.

It happened at 6.30 in the morning of August 22 as the Dragoons were near a road north of Mons.

They saw a group of Germans – and quickly gave chase.

Recalling the event 75 years later, Ben said: “The Germans began firing at us while we were still mounted... Several men dashed for cover, lying flat on their stomachs behind trees. Glancing up the road, I saw several Germans.

"They made a perfect target and Corporal Thomas, the first into action, shot one from his horse. It was my job to take the reins of three horses and get them out of harm’s way.

"I made for a high garden wall and I, among others, rode through a gate to safety, although the last horse got a ­bullet in his stomach.”

Two days later 1,000 Dragoons took part in one of the last great cavalry charges in history.

Ben recalled: “We were closely packed together and dense volumes of dust were kicked up, choking us and making it impossible to see beyond the man in front.

“All around me, horses and men were brought hurtling to the ground amid fountains of earth or plummeting forwards as a machine-gunner caught them.”

Ben’s horse was killed under him and he was lucky not to be impaled on his sword. He grabbed a riderless horse and rode to safety, grabbing a wounded comrade as he went.

Ben took part in the first Battle of Ypres in October 1914 and the Second Battle of Ypres in May 1915 – when a close pal died in his arms.

Soon afterwards he was gassed and sent home.

But by 1916 he was back, fighting alongside de Wiart on the Somme.

In 1917 Ben was wounded in the head but stayed at the front, serving at Arras and in the hellish mud of the Third Battle of Ypres.

In 1918 he was part of the Allies’ final push.

And on Armistice Day – November 11 – he was just a few miles from where he’d begun four years earlier.

In all that time, he’d been given only one leave home.

Richard said: “Ben’s story is remarkable not just because he was so young but because he’s one of the few who could claim to have served in every calendar year of the war on the Western Front.

“I’ve been lucky enough to interview more than 270 veterans of the war but he was the only one to have gone through from the opening day to the very end.”

Richard, who accompanied Ben back to battlefields including Ypres in 1990, said: “He never forgot the war but he never let memories of the horror he saw impinge upon the rest of his life.”

Just before he died aged 92, dad-of-two Ben, of Reading, Berks, said: “I was just a young lad who was crazy to be a soldier. I never regretted serving my country.”